Damper regulator



J. P. KRIECHBAUM ET AL 2,184,701

DAMPER REGULATOR Filed Jan. 2, 1956 I a w w Patented Dec. 26, 1939PATENT OFFICE omen REGULATOR John P. Kriechbaum and Carl G. Kronmiller,

Minneapolis, Minn., assignors to Minneapolis- Honeywell RegulatorCompany, Minneapolis, Minn., a corporation of Delaware ApplicationJanuary 2, 1936, Serial No. 57,221

2 Claims.

Our invention relates to a new and novel damper regulator, and moreparticularly to one in which means are provided for moving the dampersto afiring position when desired.

In systems for the automatic control of furnaces it is common to employa damper motor for actuating the dampers, which damper motor is underthe control of some condition responsive device, such as a roomthermostat. In such systems the dampers are usually moved from aposition wherein the check damper is open and the draft damper is closedto a position I in which the opposite condition exists, depending uponwhether the temperature or other control-- ling condition is above orbelow the desired value. In firing a furnace, it is necessary that thecheck damper be closed to prevent the escape of smoke from the firingdoor during the firing operation.

In certain types of furnacesit is, furthermore, necessary that both thecheck door and the draft door be closed during this firing operation.It, accordingly, is common to provide means in the basement for movingthe dampers to a position in which either the check damper alone or bothdampers are closed. Such, means commonly takes the form of a basementswitch which causes the motor to run until the dampers are in thedesired position. The objection to this arrangement is that the furnaceattendant will quite likely forget to 'move the basement switch back tothe position under which the furnace is under the control of the roomthermostat. Various complicated arrangements have; accordingly,beenprovided for returning the damper motor 35 to the control of theroom thermostat a predetermined period of time after the switch has beenmoved to firing position. These arrangements not only greatly add-to theexpense of the damper motor but rely upon timingmeans which tend to getout.of order I Another class of damper motors is provided with means fordeclutching the damper actuating arm from the motor so as to permit thedampers being manually moved to any desired firing position. In thisclass of motors, provision has been made for automatically returning themotor 1 to the control of the condition responsive'device by causing theact of declutching to energize the motor and run the same to a, positionwherein the damper actuating device was automaticably reclutched withthe motor and was returned to automatic control. One difficulty withthis type of device is that it involves more effort upon the" part ofthe operator. 'A further and even more serious objection is that thepresence of the furnaceand a room thermostat.

' such movement has been initiated.

A further object of the present invention is to provide a damper motorhaving a manual 10 switching means for causing the motor to rotate thedampers through a desired firing position and to continue such rotationuntil the dampers have reached a position determinedtby the value of thecontrolling condition. e

Other objects of the invention will be apparent from the accompanyingdescription, claims and drawing.

The single figure of the drawing schematically shows our damper motorassociated with a 20 Referring to said drawing, a conventional furnaceis indicated by the reference numeral II. This furnace is shown as beingof the hot air type, although it is to be understood that it may be ofany conventional form. The furnace is shown as hav ing the usual hot'air pipes l2, a stack pipe iii, a fuel door H,. a draft door l5 and acheck damper IS.

The damper motor comprises a motor I! having a rotor l8 and a fieldwinding IS. The motor is connected through reduction gearing 20 with ashaft 2|. The shaft 2| is provided at its opposite ends with crank arms22 and 23. Crank arm 22 is connected through a chain or'equivalent de- 5vice 24 with the draft damper l5, and crank arm 23 is similarlyconnected through a chain 25 with the check damper l6. It will be notedthat the chain 24 is provided with a certain amount of slack when thecrank 22 is in its downward switch arms 30 and 3|, respectively. Switcharm 30 is adapted to move-into engagement with a contact 32 and switcharm 3| is adapted to be moved into engagement with either contact 33 ora contact 34. Switch arms 30 and 3t and their respective contactsconstitute what may be termed a maintaining switch, the function ofwhich will be apparent from the following de- Gr1pt1on, The cam '21 isprovided with two cam toes and 36 spaced at points 180 apart, so thatswitch 36 is separated from contact 32 every 180 of rotationof shaft 2|.Cam 28 is provided with an elongated cam toe 31 which is adapted to holdswitch arm 3| in engagement with contact 34 during a considerable periodof rotation of shaft 2|. The toe 31 of cam 28 is so located that switcharm 3| is moved to the position wherein it is in engagement with contact34 before the cam toe 35 is operative to move contact 36 out ofengagement with contact 32.

Power for actuating the motor is supplied by a step-down transformer 38having a line voltage primary 39 and a low voltage secondary 46. Theprimary 36 is connected to line wires 4| and 42.

The thermostat which controls the operation of the damper motor isdesignated generally by the reference numeral 43. This thermostat is ofa conventional form and comprises a bimetallic element 44 to which isattached contact arm 45. Contact arm 45 is adapted to be engaged witheither contact 46 or contact 41. The bimetallic element is so designedthat upon the temperature dropping below the value desired the contactarm .45 will be moved into engagement with contact 46, while upon thetemperature rising to the desired value the contact arm will be movedinto engagement with contact 41. Thus, contact 46 may be referred to asthe "cold contact and contact 41 as the hot contact. While we have showna room thermostat as a controlling condition responsive switch, it willbe understood that any other suitable form of controlling conditionresponsive switch may be employed. Thus a device which is responsive tothe water temperature in the case of a hot water heating system, or tothe steam pressure in the case of a steam heating system, may beemployed.

A basement switch is generally designated by the reference numeral 48.This switch is shown as comprising a stationary contact 49 and a movableswitch blade 56. The switch blade 56 is mounted on a rotatable member 5|which may be provided with a knob 52 for conveniently rotatin member 5|manually to bring the switch arm 56 into en agement with contact 46, asshown in dotted lines in the drawing.

As shown in the drawing, our damper con trnller and the various membersassociated therewith are in the position assumed when the temperature inthe room is at the desired value. In this position, the draft damper I5is closed and the check damper I6 is open so that the dampers are'actingto retard a draft in the furnace. With the dampers in this position, acondition will eventually be reached wherein the temperature adiacentthe thermostat 43 falls below the desired value. Upon this taking place,contact arm 5 will be moved into enga ement with contact 48. This willcause the following circuit to be established through the field windingIQ of the motor l1: From one end of secondary 46, throu h conductor 53.bimetallic element 44. contact arm 45. contact 46, conductor 54. contact34, switch arm 3|, conductors 55. 56 and 51. field winding l9 andconductor 56 to the other terminal of secondary 46. This will causemotor IT to rotate with the result that shaft 2| is rotated in thedirection of the arrow 66. After a very slight initial rotation of theshaft 2| fswitch arm 36 will be allowed to move into engagement withcontact 32. Upon this taking place, the following maintaining circuitfor field winding I9 is established-: .From one end of secondary 46,through conductor 59, conductor 60, cont c 32,

switch arm 36, conductor 51, field winding l9 and conductor 58 back tothe other terminal of secondary 46. It will be noted that themaintaining circuit just traced does not depend upon the engagement ofcontact arm 45 with contact 46 so that even if contact arm 45 should beseparated from contact 46 after the motor has started its rotation, suchrotation will continue. This rotation of motor l1 and the resultantrotation of shaft 2| will continue until switch arm 36 is moved out ofengagement with contact 32 by the cam toe 36. By the time this takesplace, the cam 28 will be in a position such that switch arm 3| isresting upon the heel of the cam 28 so that it isno longer in engagementwith contact 34, being now in engagement with contact 33. Thus, both theinitial engergizing circuit and the maintaining circuit are interruptedso that rotation of shaft 2| and the resultant movement of the dampersis stopped unless in the meantime, contact blade 45 has moved intoengagement with contact 41. In this new position of shaft 2| crank arm22 is in its uppermost position and crank arm 23 is in its lowermostposition so that draft damper His new open and check damper i6 closed.

The new position of the dampers causes combustion to be accelerated soas to increase the temperature of the space to be heated. This willcontinue until the temperature of said space has risen sufliciently thatcontact 45 is moved into engagement with contact 41. Upon this takingplace, the following energizing circuit for field winding l9 will beestablished: From one end of secondary 46, through conductor 53,bimetallic element 44, contact arm 45, contact 41, conductor 62, contact33, switch arm 3|, conductors 55, 56 and 51, field winding l9 andconductor 58 to the other terminal of secondary 46. The establishment ofthis circuit through field winding I9 will cause rotation of 'the motori1 and the resultant rotation of shaft 2| with the result that cam 21will be moved so as to allow switch arm 36 to again move into engagementwith contact 32 after a very slight initial rotation of the shaft. Thisre-engagement of the switch arm 36 with contact 32 will result in thereestablishment of the previously traced maintaining circuit so that, asin the previous case, the motor will continue to rotate even though thearm 45 should move away from the contact 41. As in the precedingcase,.this rotation will continue for 180 until switch arm 36 is againmoved out of engagement with contact 32, the parts then being in theposition shown in the drawing. Before this separation of switch arm 36from contact 32 takes place, switch arm 3| has been moved out ofengagement with contact 33 and into engagement with contact 34 by cominginto engagementwith the toe 31 of cam 28.

The operation of the basement switch of our regulator will now bedescribed. Assuming that the parts are in the position shown in thedrawing, and it is desired to fire the furnace, the knob 52 is rotatedso as to cause member 5| to be ro- 4 tated until switch arm 56 is inengagement with contact 48 asshown in dotted lines in the drawing. Uponthis engagement taking place, the following energizing circuit will beestablished through field winding i9: From one end of secondary 46,through conductors 59 and 64, contact 49, switch arm 56, member 5|,conductors 65, 56 and 51, field winding i9 and conductor 58 to the otherterminal of secondary 46. This will cause rotation of motor i1 and. theresultant rotation of the shaft 2| so that, as in the previouslydescribed cases, where the energizing circuit is established by reasonof the engagement.

be limited to any particular speed of rotation,

it has been found satisfactory to provide a reducing gear such that itrequires two minutes for the shaft to rotate through 180". The actuationof the basement switch will, accordingly, cause the shaft 2| to beslowlyrotated with the result that damper i6 is slowly moved to a closedposition and the slack in chain 24 is slowly taken up. After acomparatively short period of time, during which the operator canbe-preparing to fire, dampers l5 and I6 will both be closed. Theoperator may now proceed to fire the furnace without any danger of smokeissuing from the fire door I4. Due to the relatively slow speed ofrotation of shaft 2| ample time is provided for firing the furnacebefore damper |5 has opened appreciably. Moreover, in the case of themajority of furnaces, no trouble is encountered with smoke issuing fromthe fire door even if the draft damper I6 is opened so long as the checkdamper is closed. Thus, assuming a two minute cycle,

such as mentioned above, the operator has two minutes in which tocomplete his firing operation between the time that check damper I6 isfirst movedto a closed position until the time that it is again movedtowards an open position.

As mentioned previously, shaft 2| is provided with a cam 29. This cam isprovided with two cam toes 66 and 61 which'are adapted to engage cam toe68 of member 5|. Thus. rotation of the shaft 2| will cause one or theother of the cam toes to move ,into engagement with a shoulder 68 onmember 5| if the member is in the position indicated in dotted lines inthe drawing, in which the basement switch 48 is closed. The engagementof these cam toes' will cause rotation of member 5| about its axis and aresultant separation of switch arm 50 from contact 49. While we haveshown the cam toes 66 and 61 as displaced from cam toes 35 and-3B of cam21, it is to be understood that cam toes 6G and 61 may be located at anydesired point so long as they are sufficiently displaced from the camtoes 35 and 36 to permit the switch arm 30 to move into engagement withcontact 32 to establish the maintaining circuit before switch arm 50 isseparated from contact 49.

The result of cam 29 moving switch arm 50 out of en agement with contact49 is that the motor. is returned to the control of the thermostat 43'.Thus, if the parts were initially in what unusual one and thatordinarily the con-' tact arm is in engagement with either contact 46 or41. Thus, ordinarily when the dampers are in the position indicated inthe drawing switch arm 45 would be in engagement with the "hot contact41. Accordingly, after the shaft has rotated and switch arm 30 wasseparated from contact 32 by engagement with the cam toe 35, theenergization of the motor would be continued by reason of an energizingcircuit being established through contact 33 and switch arm 3| so thatthe motor would continue to rotate until the dampers are again in theposition shown in the drawing. Thus, the shaft 2| would be rotatedthrough 360 during 180 of which, as explained previously, the dampersare in a position suitable. for firing. I It will be seen that we haveprovided an exvision is made for moving the dampers to a firing positionand returning the damper motor to automatic control without the use ofcomplicated declutching arrangements or timing mechanisms. It will beseen that we have provided a damper motor wherein the basement switchremoves the motor from control of the thermostat for only a short periodand returns the same automatically to control of the thermostat duringthe movement of the damper actuating device to the desired position. i

While we have shown a specific embodiment of our invention, it will beunderstood that this is for purposes of illustration and that ourinvention is to be limited only by the scope of the appended claims.

-We claim as our inventioni 1. In combination, a furnace, damperstherefor movable between draft retarding and draft producing positions,a damper actuating device, a motor, non-releasable connections betweensaid motor and said damper actuating device to cause movement of thelatter by the former, means responsive to a condition for initiatingmovement of said motor upon said condition assuming an undesired value,means for maintaining said motor in operation until the dampers haveassumed either said draft retarding or draft pro} ducing positiondepending upon the value of said condition, further motor controllingmeans norprior to actuation of said further controlling means, saidconnections between said motor and said damper actuatingdevice'including means to cause said motor to drive said damperssuflicient- 1y slowly that ample time is provided for firing while saiddampers are passing through said firing range.

2. In combination, a furnace, dampers therefor movable between draftretarding and draft producing positions, a motor, connections betweensaid motor and said dampers effective upon continuous movement of saidmotor in one direction to causelsaid dampers to be moved successivelyback and forth slowly between said draft retarding and draft producingpositions, means responsive to a condition for initiating. movement ofsaid motor upon said condition assuming: an

tremely simple damper regulator in which prov able to a second positionwherein it is operativeto initiate movement of said motor independentlyof said condition responsive means, and means driven by said motor formoving said further controlling means back to said first position aftersaid motor is under control of said maintaining means whereby said motorslowly operates both of said dampers through a firing range and, if thecondition responsive device remains in the same controlling position,back to the position occupied prior to actuation of said furthercontrolling means, the speed of movement of said dampers by said motorbeing sufliciently slow that ample time is provided for firing whi 1esaid dampers are passing through said firingrange. JOHN P. JQQIECHBAUM.CARL G. KRONMIILER.

